1. Field of the Invention
The present invention relates to valve timing control apparatus which variably controls open and closure timings of an engine valve constituted by an intake valve or exhaust valve of an internal combustion engine in accordance with a driving condition of the engine and its assembling method.
2. Description of the Related Art
A Japanese Patent Application First Publication No. 2003-113703 published on Apr. 18, 2003 (which corresponds to a U.S. Pat. No. 6,595,173 issued on Jul. 22, 2003) exemplifies a previously proposed valve timing control apparatus. In the previously proposed valve timing control apparatus, a housing in which a cylindrical housing member and a front cover and a rear plate to enclose openings of both ends of the housing member are integrally coupled together by means of a plurality of bolts is provided, a vane member fixed to an end of a camshaft is rotatably housed within the housing and advance angle oil chambers and retardation angle oil chambers are formed on an inner peripheral surface of the housing and alternately among three shoes of approximately trapezoid shapes and mutually projected from a radial direction toward an inner direction. A sprocket to transmit a torque from a crankshaft via a timing chain is integrally formed on an outer peripheral surface side of the rear plate. In addition, a lock pin is retractably projected from a sliding hole formed in an inner axial direction of one of the vanes and a lock hole is engageably disengaged from the lock pin on the inner end surface of the rear plate. Then, a hydraulic pressure drained from an electric power pump which is driven to be rotated in normal and reverse directions is selectively supplied to either of the advance angle oil chambers or the retardation angle oil chambers so that the vane member is rotated in the normal or reverse direction and a relative pivotal phase between the timing pulley and the camshaft is varied. Thus, the open and the closure timings of the intake valve are variably controlled. Furthermore, during a stop of the engine, the lock pin is engaged into the lock plate so that a relative conversion angular position of the vane member to the housing is retained at an optimum position during the start of the engine to secure a favorable restart performance.